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Abstract

6-Nitro-, 6-chloro-, 6-bromo- and 6-amino-2-benzoxazolones I have been prepared and aminolyzed with piperidine and butylamine into the respective 2-hydroxy-4-nitro-, 4-chloro-, 4-bromo- and 4-aminophenylureas II, III. pK_a values of hydroxyl group of these ureas have been determined. The aminolysis and hydroxylaminolysis mechanism of the mentioned 2-benzoxazolones is discussed on the basis of kinetic data. Reaction of the 6-substituted-2-benzoxazolones with methyl, phenyl and p-toluenesulphonyl isocyanates and N,N-dimethylchloroformamide has been used for preparation of the respective ureas V to VII of the type of 3-alkylcarbamoyl- or arylcarbamoyl-2-benzoxazolone. Hydrolysis mechanism of these ureas possessing a good leaving (3-benzoxazolone) group in alkaline medium and behaviour of anions of ureas VI in alkaline medium are discussed.